Field of the Invention and Related Art Statement
The present invention relates to an apparatus for detecting a fault on an over-head power transmission line comprising a current sensor for detecting a current passing through the power transmission line, and a judging means for receiving a signal supplied from the current sensor and judging the occurrence of the fault.
Upon the occurrence of any accident on the over-head power transmission line, it is required to detect promptly a point at which the fault has occurred in order to shorten the power-down period as far as possible and to improve the reliability of the electric power supply. To this end, there have been developed various fault locating apparatuses for detecting a position of a fault point on the transmission line. For instance, there has been developed a known fault locator in which a fault position detecting pulse is transmitted from a watching house or station onto the over-head transmission line and the position of the fault is detected by processing a pulse reflected from the fault point. However, this apparatus has a serious demerit that the gain of the pulse is attenuated extremely, particularly when the transmission line becomes long. Moreover, when the transmission system includes branch points, it is difficult to obtain the reflection pulse exactly, so that the fault position cannot be judged correctly.
In Japanese Patent Application Publication Kokai Sho 61-170,224, there is disclosed another known apparatus in which a current transformer CT is provided on the over-head ground line to detect a current passing through the ground line upon the fault and the position of the fault is detected at the watching house. However, in this apparatus, since the fault is not directly detected by measuring the current passing through the transmission line, the fault cannot be detected positively and further, at the transmission tower at which the transmission line is branched, it is difficult to judge a section of the power transmission line in which the fault has occurred.
In Japanese Patent Application Publication No. 62-55,375, there is described another known apparatus in which a current transformer is provided on the transmission tower to detect a surge current passing through the tower upon the occurrence of the accident. Since the surge current passes only through the tower at which the fault occurs, it is necessary to arrange current transformers on all towers, and thus the cost of the whole system is liable to be increased. Moreover, this known apparatus has a drawback that the current transformer cannot be easily provided on the tower depending upon the kinds of the towers.